Method and apparatus for underground tank cleaning

Abstract

A method and apparatus are disclosed which may be used in removing contaminants from underground petroleum storage tanks. A positive displacement pump and piping manifold are used to withdraw contaminants from an underground tank and pump those contaminants into a receiving drum. A startup suction valve is utilized to control the rate at which withdrawal is initiated and a bypass valve controls the rate of withdrawal from the tank as the cleaning operation is performed. A sample connection at the pump discharge provides means for determining the contaminant-to-product ratio of fluid being withdrawn from the underground tank. The bypass valve may be adjusted to maximize the contaminant-to-product ratio and minimize the loss of petroleum product.

What is claimed is: 
     
       1. An apparatus for removing contaminants from an underground storage tank, comprising: a receiving tank;   a manifold having a suction valve and a discharge valve;   a flexible suction hose for insertion into said underground storage tank, said suction hose being connected to said suction valve;   a positive displacement pump adapted to take suction through said suction valve and to discharge through said discharge valve to said receiving tank; and   a startup line adapted at one end to take a suction on liquid in said receiving tank and connected at its other end to said manifold,   the manifold including a valve means for selectively causing said pump to take suction through said discharge valve and causing said pump to discharge through said suction valve.   
     
     
       2. The apparatus of claim 1, further comprising means for varying the rate of suction of said pump through said suction valve. 
     
     
       3. The apparatus of claim 1, wherein said manifold further includes a bypass valve for controllably interconnecting the discharge of said pump and the suction of said pump. 
     
     
       4. An apparatus for removing contaminants from an underground storage tank, comprising: a flexible suction hose for insertion into said tank;   a pump for pumping contaminants from said tank to a receiving drum; and   a piping manifold for connection between said suction hose and said pump and between said pump and said receiving drum, said manifold having a bypass valve for varying the rate of suction by said pump from said tank and said manifold having a backflush valve means for alternatively connecting a discharge of said pump to said suction hose or to said receiving drum.   
     
     
       5. The apparatus of claim 4, further comprising: a startup suction line interconnecting said receiving drum and the suction of said pump; and   a startup valve interposed in said startup suction line for controlling a level of vacuum at the suction of said pump.   
     
     
       6. An apparatus for removing contaminants from an underground storage tank, comprising: a flexible suction hose for insertion into said tank;   a pump for pumping contaminants from said tank to a receiving drum; and   a piping manifold for connection between said suction hose and said pump and between said pump and said receiving drum, said manifold having a bypass valve for varying the rate of suction by said pump from said tank,   said manifold further comprising a reversing valve for selectively reversing the direction of flow through said suction hose.   
     
     
       7. An apparatus for removing contaminants from an underground storage tank, comprising: a suction hose assembly, including a guide tube for insertion into said underground tank,   a flexible hose for insertion through said guide tube into said tank, and   a hose reel for receiving and dispensing said hose;     a positive displacement pump;   a sediments receiving drum; and   a piping manifold system, including first suction and discharge valves for connection to said pump,   a connector for connection to said suction hose assembly;   a second discharge valve for connection to a discharge line terminating in said receiving drum;   a startup suction valve for controllably connecting said receiving drum to an inlet of said pump,   a bypass valve for adjusting the rate of removal of contaminants from said underground tank,   a four-way valve for selectively reversing flow produced by said pump, and   a sample tube for extracting fluid samples.     
     
     
       8. A system for removing bottom sediments and water from a hydrocarbon storage tank, comprising: a receiving tank;   a flexible suction line having a suction end and a discharge end adapted at said suction end to be lowered to the bottom of said storage tank;   a positive displacement pump having a suction and a discharge;   a first flow line connecting said discharge end of said flexible line to said suction of said pump;   a second flow line connected at a first end to said discharge of said pump and opening at its second end into said receiving tank;   a start up flow line connected at a first end to said first flow line and opening at a second end into said receiving tank;   a valve in said startup flow line; and   switching means for disconnecting said first flow line from said pump suction and connecting said first flow line to said pump discharge and for disconnecting said second flow line from said pump discharge and connecting said second flow line to said pump suction.   
     
     
       9. The system of claim 8 including a reel for reeling said flexible line into and out of said storage tank. 
     
     
       10. The system of claim 8 including a sight glass in said flexible line. 
     
     
       11. The system of claim 8 including a guide tube in said storage tank to receive and guide said flexible line into said storage tank and along the bottom of said storage tank. 
     
     
       12. A system for removing bottom sediments and water from a hydrocarbon storage tank, comprising: a receiving tank;   a flexible suction line having a suction end and a discharge end adapted at said suction end to be lowered to the bottom of said storage tank;   a positive displacement pump having a suction and a discharge;   a first flow line connecting said discharge end of said flexible line to said suction of said pump;   a second flow line connected at a first end to said discharge of said pump and opening at its second end into said receiving tank;   a start up flow line connected at a first end to said first flow line and opening at a second end into said receiving tank;   a valve in said startup flow line; and   a four-way valve in said first and second flow lines which in a first position provides a first flow path from said flexible line through said first flow line to said suction of said pump, and a second flow path from said discharge of said pump through said second flow line to said receiving tank; and in a second position provides an alternate first flow path from said receiving tank to said suction of said pump and an alternate second flow path from said discharge of said pump through said second flow line to said flexible line.   
     
     
       13. A system for removing bottom sediment and water from a hydrocarbon storage tank, comprising: a first flow line having a first end and a second end and adapted at said first end to be lowered to the bottom of said storage tank;   a receiving tank;   a second flow line having first and second ends, said first end extending near the bottom of said receiving tank;   a flow loop, including a positive displacement pump, a suction line having first and second ends and attached at its second end to the suction of said pump, and a discharge line including first and second ends and attached at its said first end to the discharge of said pump; and   a two-position, four-way valve connected to said loop and said second ends of said first and second flow lines such that said valve in a first position establishes flow between said second end of said first flow line and said first end of said suction line, and between said second end of said discharge line and said second end of said second flow line, and such that said valve in a second position establishes flow between said second end of said first flow line and said second end of said discharge line, and between said first end of said suction line and said second end of said second flow line.   
     
     
       14. The system of claim 13, further comprising: a startup flow line having first and second ends, said first end near the bottom of said receiving tank and said second end connected to said suction line between said four-way valve and said pump; and   a startup control valve in said startup flow line.   
     
     
       15. The system of claim 13, further comprising: a bypass flow line having first and second ends, said first end connected to said discharge line between said pump and said four-way valve, and said second end connected to said suction line between said four-way valve and said pump; and   a bypass control valve in said bypass flow line.   
     
     
       16. A method for removing contaminants from an underground storage tank, comprising the steps of: initiating fluid flow by pumping fluid from a receiving tank;   gradually closing a startup suction valve to increase a pumping vacuum and decrease fluid flow from said receiving tank;   pumping contaminants from said storage tank; and   controllably adjusting the rate at which contaminants are pumped from said storage tank.   
     
     
       17. The method of claim 16, wherein a bypass valve is manipulated to controllably adjust the rate at which contaminants are pumped from said storage tank. 
     
     
       18. The method of claim 16, wherein said startup suction valve is manipulated to controllably adjust the rate at which contaminants are pumped from said storage tank. 
     
     
       19. The method of claim 16, wherein said pumping is accomplished using a positive displacement pump. 
     
     
       20. The method of claim 16, wherein the step of adjusting the rate comprises the step of controllably interconnecting the pump discharge and suction to regulate the rate at which contaminants are pumped from said storage tank. 
     
     
       21. A method for removing bottom sediments from an underground tank, comprising the steps of: initiating fluid flow by pumping fluid from a receiving tank;   gradually closing a startup suction valve to increase a pumping vacuum and decrease fluid flow from said receiving tank;   pumping bottom sediments from said underground tank through a suction conduit;   controllably interconnecting a discharge and a suction of said pump to regulate the rate at which bottom sediments are pumped from said underground tank; and   selectively reversing the flow through said suction conduit.